Many electronic systems, such as computer systems, need one or more power supplies for operation. In some such systems, the power supplies need to supply a large amount of power while minimizing the volume used to house the power supply components. Such power supplies often include a primary circuit interfacing with mains power and including a switching circuit to provide a source of a relatively high voltage, and a secondary circuit to convert the relatively high voltage into one or more relatively low voltage sources for powering circuitry. The power supply is generally enclosed in an enclosure having openings for air flow at its front and back.
Such power supplies often contain fans or blowers or other air flow generators located at one end of the structure housing the electric power components. These generators create a flux of air at the side of the structure having the generator.
Typically, the power supply electronic components generate relatively large amounts of heat in operation. These components are typically coupled to heat sinks in the power supply structure. As an airflow comes into contact with these heat sink structures, heat is transferred from the heat sink to the air. The air is then propelled out of the structure and into the environment, thus cooling the power supply.
The force imparted on the atmosphere at either end of the air flow generator tends to dissipate as the distance from the airflow generator increases due to thermodynamic and kinetic loss of energy in the flowing air. Accordingly, using a conventional architecture, a strong flow of air typically cannot be maintained throughout the power supply structure containing the power supply electronic components.
In some cases, the airflow generator is placed towards the “front” of the power supply unit. In such power supplies, the airflow at the “back” of the supply is reduced due to the kinetic energy loss of the airflow through the unit. In typical applications, an airflow generator creates a pressure differential at a particular location, resulting in an inflow into the generator and an outflow from the generator. The environmental impedance of the components within the enclosure produces an effective drop in the differential pressure created by the airflow generator. In the case described above, the airflow at the “back” is correspondingly reduced by the amount of the air flow impedance of the components and their heat sinks and other associated circuitry and parts disposed within the enclosure. The effective flow rate is the lesser of the rates at the opposing input and output ends with the effects of the air flow impedance of the components acting to reduce the pressure differential.
Accordingly, a lower airflow at an exhaust port may result in less heat per unit time being removed from the power supply. This limits the performance of the power supply. Greater air flow means that components can be run at higher power dissipation levels, the size of the power supply can be reduced, and/or performance can be increased.
In some cases, the airflow generator is placed towards the “back” of the power supply unit, e.g., near the exhaust port. In such power supplies, the airflow at the front end or intake port of the power supply can be reduced based on the kinetic energy loss of the airflow through the supply and on the increased impedance of the drop applied across the entire length of the enclosure. The increased impedance is reflected in a lower airflow. Accordingly, a lower exhaust airflow results in a lower intake airflow being drawn into the enclosure. Similar performance is reduced over what can be achieved with greater air flows.
Accordingly, an architecture for improving the performance of an air flow-cooled power supply would be desirable.